Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2002-08-30
2003-06-03
Kwok, Helen (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
Reexamination Certificate
active
06571634
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods of ultrasonic inspection of long-distance pipelines, mainly trunk oil pipelines, oil-products pipelines and gas pipelines, while providing acoustic communication between the ultrasonic sensors and the pipe walls (for example, with the help a so-called “pig” or a scanning device which is put into the pipeline and transported under power of the fluid flow in the pipeline). The inspection pig has built-in sensors, means for measurement, conversion and recording of the measured data and a device for collecting the digital data in the process of pig travel and for processing the obtained data to detect the flaws in the pipe walls and to determine the parameters of the detected flaws, as well as their location in the pipeline.
2. Description of the Related Art
Known in the art is a method of in-tube ultrasonic inspection [RU2042946, RU2108569, U.S. Pat. No. 4,162,635] effected by passing inside a pipeline a scanning pig having ultrasonic sensors, measuring means for measurement, processing and storage of the measured data. During the pig travel ultrasonic probing pulses are emitted towards the walls and the respective reflected ultrasonic pulses are received.
Also known in the art is a method of in-tube ultrasonic inspection [WO96/13720 (relevant patent documents: U.S. Pat. No. 5,587,534, CA2179902, EP0741866, AU4234596, JP3058352), EP0304053, (relevant patent documents: U.S. Pat. No. 4,964,059, CA1292306, NO304398, JP1050903), U.S. Pat. No. 5,062,300 (relevant patent documents: CA1301299, EP0318387, DE3864497, FR2623626, JP2002923), U.S. Pat. No. 5,460,046, (relevant patent documents: EP0684446, JP7318336), EP0271670 (relevant patent documents: U.S. Pat. No. 4,909,091, CA1303722, DE3638936, NO302322, JP63221240), EP0616692, (relevant patent documents: WO9312420 U.S. Pat. No. 5,635,645, CA2125565, DE4141123, JP2695702)] by passing inside the pipeline a scanning pig accommodating ultrasonic sensors, means for measurement, processing and storage of the measured data, and by emitting ultrasonic probing pulses during the pig travel and receiving the ultrasonic pulses reflected from the internal and external walls of the pipeline, the run time of the above pulses being measured.
These methods allow one to find out corrosive flaws such as loss of metal and scaling and to determine the parameters of these flaws. However, to detect crack-like damage of the pipe wall and to determine their depth, one needs information on the amplitudes of the received pulses. The absence of such an information in the above methods does not allow one to use these methods for crack detection.
Known in the art is a method of in-tube ultrasonic inspection of pipelines [RU2018817] effected by passing inside the pipeline a scanning pig carrying ultrasonic sensors, means for measurement, processing and storage of the measured data, emission of ultrasonic probing pulses during the pig travel and reception of the reflected ultrasonic pulses corresponding to the probing pulses with the help of said ultrasonic sensors, amplifying the output electric pulses of the sensors corresponding to the received ultrasonic pulses, converting and storing the measured data.
This method is characterized in that a mirror ultrasonic pulse is separated from the received ultrasonic pulses depending on the arrival time, the electric pulses corresponding to the separated mirror ultrasonic pulses are converted into a control voltage depending on the amplitude of the mirror pulse, and the control voltage is used to control the amplification of the pulses reflected from the flaws.
An advantage of this method is that it allows one to correct the errors when measuring the amplitudes of the pulses arising due to the acoustic attenuation in the depositions on the inner wall of the pipeline, the thickness of these depositions being different in the different sections of the pipeline.
The main disadvantage of the above method is that the method is practically inapplicable for reception of ultrasonic pulses subjected to multiple reflections because it is practically impossible to separate “on-line” mirror pulses with preset parameters among all repeatedly reflected ultrasonic pulses for generating a control voltage. Besides, in the given method no account is taken for the attenuation of the ultrasonic pulses in the pipe wall and the losses due to the partial penetrability of the media interface during the multiple reflections in the pipe wall.
The prior art of the proposed invention is a method of in-tube ultrasonic inspection of pipelines [U.S. Pat. No. 5,497,661 (relevant patent documents: WO9210746, EP0561867, CA2098480 DE4040190)] by passing inside the pipeline a scanning pig comprising ultrasonic sensors, means for measurement, processing and storage of the measured data, including the steps of emission of ultrasonic probing pulses during the pig travel and reception of the reflected ultrasonic pulses corresponding to the probing pulses, using the same ultrasonic sensors, amplification of the electric pulses from the sensors, corresponding to the received ultrasonic pulses, conversion and storage of the measured data.
This method is characterized in that it includes reception of at least one ultrasonic pulse reflected from the inner wall of the pipeline and at least two ultrasonic pulses reflected from the external wall of the pipeline, the reflected pulses being picked up by at least one ultrasonic sensor and amplified.
To receive the pulses after emitting the probing pulse, a time window is created having such a width that the pulse reflected from the inner wall of the pipeline and the two pulses reflected from the external wall of the pipeline are within the window, the received pulses being digitized.
The digitized pulses are filtered and parametrized. The maximum time and amplitude are determined for each reflected pulse and compared with a digital threshold value.
The width and amplitude of the reflected filtered and parametrized pulses are sent to a computer module, in which the parametrized pulses are processed to determine the time between the arrival of the nearest pulse reflected from the external wall of the pipeline and the arrival of the pulse reflected from the inner wall thereof. The parametrized pulse whose amplitude is higher than or equal to the amplitude of the previous pulse is recorded.
The time of the pulse generation and the time of its run in the pipe wall are determined and recorded if the time slot between the ultrasonic pulse reflected from the pipeline inner wall and the first pulse reflected from the pipeline external wall coincides within an allowable limit with the time slot between the first and second pulses reflected from the external wall of the pipeline. In so doing all parametrized pulses, for which said time slots do not coincide within the allowable limit are recorded.
In this method both the time from the moment of emission of the probing pulse to the moment of reception of the reflected pulses and the amplitude of the reflected pulses are measured and this is a necessary condition for detection of cracks in the pipe wall. However, the crack detection is effected using ultrasonic pulses emitted at some angle (about 17°) to the normal of the inner wall of the pipeline and reflected from the crack forming a corner reflector with the internal or external wall of the pipeline. In this case, a crack-like flaw corresponds to one reflected ultrasonic pulse, and the application in the prior art condition of coincidence of the time slots between the multiple reflected pulses is inefficient. Besides, the amplitudes of the multiple reflected ultrasonic pulses decrease depending on the total thickness of the metal layer penetrated by the pulse and on the amount of reflections from the media interfaces.
An advantage of the prior art method is that the digital threshold v
Bazarov Alexandr J.
Chernov Sergei V.
Desyatchikov Alexandr P.
Desyatchikov Denis A.
Eliseev Vladimir N.
Bellamy Tamiko
Kwok Helen
NGKS International Corp.
Quarles & Brady LLP
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